Solvent refining of lubricating oil



Marh 16, '1937. J. DEARBORN E-r AL 2,074,254

SOLVENT REFIN'ING OF II IUBRICTIIIIGr OIL Filed May 1o, 1934' zal /4//7//4/72 P lec INVENToRs Patented Maf; le, 19s? I UNITE '.srArEs.

PATENT oFFlc Gee, Plainfield, N. J., Company, New York,

Delaware assignors to The Texas yY., a corporation oi' Application May 1o,'1934,'seria1 sie. 724,840

. l Claim.

i 'With solvents, for the production of lubricating The invention contemplates a process of ren' 5 ing minerl oil containing so-called naphthenic and parailinic, including wax, constituents where-y in the oil is extracted to remove the naphthenic constituents and thereafter dewaxed with a suitable selective solvent liquid or liquids in the presence of the same diluent or modifying solvent liquid.

More specifically, the invention contemplates diluting the oil with a solvent liquid of the character of benzl, one of its homologs,v a. mixture of benzol or its homologs, or a low-boiling petroleum fraction of the character of propaneand butane. This dilute mixture is then extracted with an extraction solvent comprising furfural whereby the mixture is separated into a parafiinic phase and a naphthenic phase.` The parailinic phase or raiilnate portion comprises the paramnic constituents including wax mixed with the bulk lof the diluent solvent liquid and some furfural, while the naphthenic phase -or extract portion comprises the naphthenic constituents of the oil dissolved in furfural and some oi the diluent solvent liquid. y

The rainate mixture. after separation of the extract, and without stripping any of the diluent l' 430 from the raillnate, is subjected to cooling for the purpose of `separating all or a portion ofthe furfural contained therein land which is thus recovered for reuse in the extracting step.

The remaining mixture comprises mainly waxbearing oil and a large proportion of 'the original liquid which is adapted Yto be used in both the A extraction and thedewaxing steps; and thereby avoiding any necessity forqstripping the `diluent ,l v prior to .dewaxingl The use `of a'diluent during the extraction step is of particular advantage in that a. more effective contact between extraction isolvent and oil is realized when the oil is in a' dilute `state. The separation or the mixtiueinto, naphthenic and Paramnlc layers is also more readily lfacilitated in the case of a dilute mixture.

It is, therefore, an object of the invention to employ, as the diluent in the extraction step, one which will also provide, when mixed with a suitablewax anti-solvent liquid, a satisfactory se- 5 lective dewaxing solvent mixture.

In order to more clearly describe the invention, i reference will now be made to the accompanying drawing forming a part of this specf'iication. The oil to be refined which, for example, may bel a residual wax-bearing cylinder stock fraction, derived from Mid-Continent crude, is conducted from a tank i'to a mixer 2 wherein it is mixed with benzol from tank 3. The proportions used may comprise about three parts of benzol to four parts of oil, although it is to be understood that, depending upon the ,nature of the oil undergoing treatment, these proportions may be reversed, so

` that the proportion of benzol to-'oil used may be considerably greaterf` For example, it may be 20 The' furfural is conducted vfrom a tank 5 to k30 lthe upper portion of the chamber il. The furiural is advantageously introduced to the extracting chamber at a temperature of around 225 F. It may, therefore, be necessary to warm the furfural by passage through a heater prior to introduction to the extracting chamber. lin some instances, it may be desirable to cool the furfural, particularly where the furfural has been stripped from previously Lextracted oil and is still hot. In that case, instead of passing the furfural through the heater 6, it may be cooled by passage through a cooler 'i' prior to introduction to theextracting chamber:

The temperature at which the extraction solvent is introduced to the extraction chamber will, of course, depend upon the particular tem- '.perature conditions which it is desired to maintain within thechamber. Usually, it may be desirable to maintain a temperature of around 180i F. Aat the top ofthe chamber, with a temperature of about 15G F. at-the bottom. `Il it is desired to maintain diherent, or reverse, temperature con- 4ditions, then the furfural may beintroduced at a correspondinglyidiierent temperature, ranging,

for exampleLfrLom 1 50'to 300.F. The ratio of 55 furfural to dilute oil may comprise about two parts of furfural to one part of dilute oil.

The furfural coming into contact with the dilute oil within the extracting chamber 4 dissolves the naphthenic constituents, forming an extract portion, which is withdrawn from the bottom of the chamber through an outlet 8 to a tank 9.

The parainic constituents, together with the bulk of the diluent solvent and a relatively small proportion of the furfural, are removed from the top of the extracting chamber through a pipe I to a cooling coil II. This mixture may be cooled to a temperature of around 90 F. or lower, whereupon a substantial proportion of the furfural separates from the mixture due to its insolubility therein at low temperatures. n

The cooled mixture is introduced to a settler I2 wherein the furfural is separated, withdrawn through a pipe I3, and conducted to the solvent tank 5 for further use.

The remaining mixture, comprising mainly wax-bearing oil and benzol, in the proportions roughly of about two parts or more of benzol to three parts of oil, is conducted from the settler I2 to a mixing coil I4, wherein it is mixed with acetone or other suitable wax anti-solvent liquid from a tank I5.

Additional quantities of diluent solvent may be added where necessary from tank 3 through a pipe I6. In this way, a suitable dewaxing mixl ture, containing around 35% of acetone and 65% benzol, in the proportion of around three parts of acetone-benzol mixture to oil is formed.

'This mixture is then conducted through a chiller I1 wherein it is chilled to a temperature of around F. in order to solidify the wax. The cold mixture, containing suspended wax, is conducted through a pipe I8 to a filter I9 wherein the wax is removed as a filter caketo produce a dewaxed filtrate. The wax is accumulated in the tank 20 while the dewaxed filtrate accumlates in The solvents may be recovered from the wax and filtrate by distillation or stripping with steam or any other suitable method and thus recovered for reuse.

If desired, the ltration may be carried out i the presence of a'suitable filter-aid material such as diatomaceous earth, fullers earth and the like. In .that case, the chilled mixture is conducted from the chiller I1 directly to a mixture 22 wherein it is mixed with filter-aid material contained in the vessel 23. The resulting mixture, containing solid wax and lter-aid material, is then charged into the lter I9.

While benzol has been described as the diluent solvent in the foregoing example, itis contemplated that other diluent solvents,- such as propane or butane, may be used. Where normally gaseous material, such as propane, is used, it will be necessary to employ a closed system capable of withstanding suiiicient pressure in order to maintain the diluent'in a liquid condition.

Also, While the extraction step has been described as a continuous countercurrent operation, itis contemplated that intermittent extraction of the batch type may also be employed.

'Ihe invention is not restricted to the particular -operating conditions described in the foregoing example since the temperatures therein set forth, as well as the proportion of solvents used, may be varied, depending upon the nature of the oil undergoing treatment.

Furthermore, the invention is not limited to the treatment of residual cylinder stock fractions but is applicable to either distillate or residual oils, whether viscous or relatively non-viscous, and

' irrespective of the source of the oil. l

Obviously, many modifications and variations of the invention, as hereinbefore set forth, may be made without departing from the spirit and scope thereof, and therefore only such limitations should be imposed as are indicated in the appended claim.

We claim:

In the manufacture of lubricating oil of low pour test and high viscosity index from viscous wax-bearingmineral oil, the method which comprises diluting wax-bearing oil comprising constituents of cylinder stock viscosity,.extracting the dilute mixture with furfural at a temperature of around 150 to 300 F. and substantially above the solid point of the wax constituents, formingy an extract phase containing low viscosity index constituents and a. raffinate phase comprising high viscosity index oil, Wax, some furfural and diluent liquid, cooling the raffinate phase to a temperature of around 90 F. to separate furfural therefrom, removing the portion of furfural so separated, mixing the remaining mixture of rafiinate oil, wax and solvent with a further quantity of diluent and aliphatic ketone, such as acetone and methyl ethyl ketone, in proportions such that the solvent mixture has selective action as between oil and wax at a temperature of around 0 F., chilling the mixture to a temperature of 0 F., lbelow to precipitate the wax, and removing the wax so precipitated.

RICHARD J. DEARBORN. WILLIAM P. GEE. 

